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Drilling in Position—

therefore can perform no fewer than four operations—flue-hole
cutting, oval manhole cutting, tube drilling or other single
drilling, and boiler-end turning.

Although the foregoing is a very useful, it is by no means a
usual tool. The rotating table is more often placed on a bed by
itself, constituting a vertical face lathe/

Drilling in Position.—The plates of a cylindrical boiler
being prepared and temporarily connected, the rivet holes are
drilled right through the several plate thicknesses. If stationary
machines are employed they must be supplied with a cradle or
bed on which to lay the boiler, so that the latter may be turned
round on its axis, and thus present all portions of its surface
at various times to the drill. Obviously there are two principal
ways in which the axis may be placed, vertically and horizontally,
the latter being used for large marine boilers, while the former is
advantageous when drilling locomotive or Lancashire boilers,
though it has also been employed for marine work.

Drills with Boiler Axis vertical.—Fig. 292 illustrates
this type of drill: and its individual application (the drilling of
rivet holes in the flanges of boiler flues), will first be described.
The machine is the design and patent of Messrs. Geo. Booth &
Co., and is very ingenious throughout The flue is bolted, with
its axis vertical and central, upon the circular table A, and a
handwheel B, being connected to the table by bevel gear c and
worm gear D, serves as a dividing plate, its revolutions being
counted to turn the flue through any fraction of its circumference
between each operation. The saddles E F ride upon vertical
standards G H, and contain horizontal slides j K, for adjustment to
various diameters. / is the driving cone, and power is taken from
horizontal shaft L by mitre gear to the vertical shafts M and N :
from these the various motions are obtained. Thus the spur gear
and mitre gear at o and p give motion to the horizontal spindles
Q R, and from thence by mitre gear to the vertical spindles s T,
which turn the drills u u and v v by spur gear. The vertical
movement of the saddles is given by hand or power. When by
power, a worm on shaft N gears with worm wheel w, which
actuates a second worm and wheel at x, connected with the screw
Y by mitre gear. The mitre wheel on Y rotates within a boss cast